The present invention relates to a single-substrate-heat-treatment apparatus for heat-treating the target substrate one by one in a semiconductor processing system and, more particularly, to a heat-treatment apparatus which uses a light source as a heat source for the target substrate. The term "semiconductor processing" used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target substrate, such as a semiconductor wafer or an LCD substrate, by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target substrate.
As an apparatus for performing a predetermined process while heating a target substrate, such as a semiconductor wafer, one by one, a single-substrate film formation apparatus and an annealing apparatus are known. In a heat-treatment apparatus of this type, a strong resistive heater or a plurality of strong heating lamps are disposed above or below the wafer so as to heat the wafer in a process chamber.
The single-substrate-heat-treatment apparatus is required to heat and cool a wafer at high speed. This is because the single-substrate-heat-treatment apparatus processes wafers one by one, while a batch heat-treatment apparatus simultaneously process nearly 100 wafers. To obtain equivalent throughput, the single-substrate-heat-treatment apparatus must make heat and cool at a speed 100 times that of the batch heat-treatment apparatus.
The technical difficulty upon constructing the single-substrate-heat-treatment apparatus lies in that high planar uniformity of wafer temperature must be realized while providing high heating/cooling performance that can assure high throughput. For example, if the apparatus is covered by a heat-insulating material, high uniformity of wafer temperature is assured but cooling performance impairs, thus obstructing the function of the apparatus. For this reason, the single-substrate-heat-treatment apparatus requires a combination of a heat source having high heating performance and a chamber having sufficiently high cooling performance.
In a conventional single-substrate-heat-treatment apparatus, not only a wafer but also a work table having higher heat capacity than the wafer must be heated to a predetermined process temperature, and must be cooled immediately upon completion of the process. Hence, most of electric power consumed is wasted. For example, in the conventional single-substrate-heat-treatment apparatus, electric power as high as 40 to 50 kW must be input upon heating. Also, upon cooling, a considerably long time period is required since the work table must also be cooled, resulting in low throughput.
The resistance to heat conduction between the wafer and work table has a large variation that depends on their local contact states. Such variation seriously disturbs the planar uniformity of wafer temperature. Also, when the temperatures of internal structures other than the wafer, such as the work table, the inner wall of the process chamber, a shower head for supplying a gas, and the like rise, reaction products also adhere to these internal structures (especially, in a film formation process). Such reaction products increase the frequency of maintenance such as cleaning.
Furthermore, the single-substrate-heat-treatment apparatus is required to have high planar uniformity of wafer temperature. If the planar uniformity of wafer temperature is low, the conductivity of a crystal obtained by annealing varies, the thicknesses of films formed have variations, and so on. To prevent this, it is important for the a process accompanying wafer heating to maintain high planar uniformity of wafer temperature.
In the conventional single-substrate-heat-treatment apparatus, for example, a plurality of thermocouples (e.g., three thermocouples at positions corresponding to the center, middle portion, and outer periphery of the wafer, or a large number of thermocouples over the entire wafer surface) are disposed to measure the wafer temperature. Based on the measurement results, inputs to be given to resistive heaters or heating lamps corresponding to the nonuniform wafer temperature portions are controlled, thus maintaining high planar uniformity of wafer temperature.
However, even when a given temperature distribution in the wafer surface is detected using several or a large number of thermocouples, such temperature distribution is a very rough one. In a conventional heating mechanism using resistive heaters or heating lamps, the heat input amounts can be controlled in units of a heater zone or individual lamps, but each area to be controlled is too broad to control the temperature of a specific portion.